1. Field of the Invention
The present invention relates to a hot runner manifold for multi-cavity injection molding. The manifold is constructed in such a way that not only can it achieve a good balance-flow for each drop because of its simple structure, but it also has a low production cost. And it provides an easy method for maintenance when cleaning the manifold is required.
2. Description of the Prior Art
FIG. 1 is a simple chart which shows a runner system inside a unbalanced manifold. FIG. 1, it shows resins coming from the nozzle of an injection molding machine into the inlet of the manifold (12). The resins then pass through a runner passage flow (21). The manifold has four outlets ((13-A1), (13-A2), (13-A3), (13-A4)).
From the situation described above, there is a unbalance flow, because the pressure of resin inside the 13-A1 and 13-A3 isn""t equal to the pressure of resin inside 13-A2 and 13-A4. This results in an unequal quality of product for each drop.
In order to have equal quality, manufactures try to produce manifolds which have a balanced flow structure. Like FIG. 2, after the inlet 12 and the runner passage 21, there is a sprue runner 23 and the runner passage 22. There are also the outlets 13-B1, 13-B2, 13-B3, 13-B4. From the flow chart, it can be seen that there will be the same pressure of resin action within the 4 outlets. For the outlets having more than 8 drops, such as 12 drops, FIG. 5 shows this in a simple balance flow chart. In real use, the traditional manifold is made like FIG. 6. There are a lot of plugs which have to be done to change the direction of the runner passage in order to achieve balance flow. This method makes a multi-drops manifold in elongated directions. Not only does it become very complicated when it is machined, but it is also very difficult to be achieved, because too many plugs need to be completed.
Also when the runner passages inside the manifold have to be cleaned, it is very difficult to complete this work. Hence, the inventor has found it necessary to invent a good structure which not only has a simple way to make a manifold but also can have easily maintained.
U.S. Pat. No. 5,762,976 to Paul shows a manifold for thermally sensitive resins that appears to be well-balanced and have corners in multi-drops manifold. But it is very complicated to manufacture. Also it is very difficult for the multi-drops to have more than 8 outlets in an elongated direction. For example, U.S. Pat. No. 4,761,343 to Gellert, focuses on a balance flow manifold system with bridging manifold which extends transversely across a number of spaced elongated support manifolds. It does not mention how to produce an easy way to make a multi-drops manifold for an elongated direction. The U.S. Pat. No. 6,007,108 to Ewikon, shows the distribution plugs for use with a nozzle manifold of a hot runner injection molding system. It is totally different from the present invention, because the present invention is a manifold without any plugs, U.S. Pat. No. 5,804,231 to Philip shows a manifold for a hot process injection molding apparatus which includes a two piece manifold for a slidable coupling in case of my expansion and contraction. The present invention differs markedly from the patent. U.S. Pat. No. 4,964,795 to Patrick which shows a manifold assembly used for conveying plastic injection molding material from a central injection point or sprue to multi-cavity. It focuses on inhibiting the heat transfer between the manifold and the core or cavity. U.S. Pat. No. 4,299,553 to Nareshwar shows a manifold formed in two pairs which includesa plate and a ring which are joined along a central parting line in a manner wherein all of the sprue and runner portions may be readily and accurately machined. It is for drops in circle location. However, the present invention is for drops in an elongated location.